On the status of the critically endangered Caspian Brown Trout, Salmo trutta caspius, during recent decades in the southern Caspian Sea basin (Osteichthyes: Salmonidae)

Abstract

The changes in some of the biological traits of mature females of the critically endangered Caspian Brown Trout, Salmo trutta caspius Dorofeeva, 1967, during recent decades were analysed. The results demonstrated that the mean length has significantly (p<0.05) declined over the past 60 years, from 77.6 cm in 1947 to 59.8 cm in 2007 (22.4%). The same trend was observed for mean total weight which significantly (p<0.05) reduced from 4880.2 g in 1947 to 2486.8 g in 2007 (49.5%). Also, the level of absolute fecundity sharply decreased from 7041.8 in 1947 to 4526.1 in 1973 and to 2941.2 in 1986. Whereas there was no significant (p>0.05) difference between the relative fecundity in 1947 (1451.4 per kg of body weight) and 1973 (1372.6 per kg of body weight), a significant (p<0.05) reduction has been observed since 1986 (1199.8 per kg of body weight). The possible reasons for these biological changes are discussed. Based on this study, the exploitation and sale must be controlled, and efforts should be concentrated on rehabilitation of the natural spawning habitats as soon as possible.

Key words:

• Caspian Brown Trout
• relative fecundity
• absolute fecundity
• length
• conservation
• Red Data Book
• threatened species